Presentation on theme: "Sources of energy. Fossil fuels. What is the alternative?"— Presentation transcript:
1Sources of energy. Fossil fuels. What is the alternative? Where do we get energy from?
2Sources of energyBefore we look at where we get our sources of energy from, we need to think about what we use it for – because once we know that, then what form this energy comes in is much clearer.What do you use energy for?What does the world at large use it for?
3We use energy sources to generate the electricity we need for our homes, businesses, schools, and factories. Electricity "energizes" our computers, lights, refrigerators, washing machines, and air conditioners, to name only a few uses.We use energy to run our cars and lorries. Both the petrol used in our cars, and the diesel fuel used in our lorries are made from oil. The propane that fuels our outdoor grills and makes hot air balloons soar is made from oil and natural gas.
4So what are the energy sources we use? Electricity is called a secondary source because it is generated from something else – what are the primary sources that you can think of that do this? What other primary sources of energy do we useTO THE WHITEBOARDI am going to write your answers in a pattern – can you see what the pattern is?
6Fossil Fuels - introCoal, oil and gas are called "fossil fuels" because they have been formed from the organic remains of prehistoric plants and animals.They still provided around 66% of the world's electrical power, and 95% of the world's total energy demands (including heating, transport, electricity generation and other uses).
7Where Fossil Fuels Come From There are three major forms of fossil fuels: coal, oil and natural gas.All three were formed many hundreds of millions of years ago before the time of the dinosaurs - hence the name fossil fuels.The age they were formed is called the Carboniferous Period.It was part of the Paleozoic Era."Carboniferous" gets its name from carbon, the basic element in coal and other fossil fuels.
9The Carboniferous Period occurred from about 360 to 286 million years ago. At the time, the land was covered with swamps filled with huge trees, ferns and other large leafy plants, similar to the picture.The water and seas were filled with algae - the green stuff that forms on a stagnant pool of water.Algae is actually millions of very small plants
10As the trees and plants died, they sank to the bottom of the swamps or oceans. Today, because it is colder and drier, the trees would fall down and rotBut then, there was lots of warm water and so they fell into the swamp. Microbes that would help them rot were not present, so they just piled up. (a bit like leaves that fall to the bottom of a pond and stay leaf-shaped but are black and slimy)They formed layers of a spongy material called peat.Over millions of years, the peat was covered by sand and clay which squashed it and turned it into rock.The peat was squeezed and squeezed until the water came out of it and it eventually, over millions of years, it turned into coalOil or petroleum and natural gas were formed from the algae and small animals in a similar way, creating liquid and gas under pressure.
13Advantages of fossil fuel for electricity Very large amounts of electricity can be generated in one place using coal, fairly cheaply.Transporting oil and gas to the power stations is easy.Gas-fired power stations are very efficient.A fossil-fuelled power station can be built almost anywhere, so long as you can get large quantities of fuel to it.Didcot power station, in Oxfordshire, has a dedicated rail link to supply the coal.
14Disadvantages of fossil fuel for electricity (1) The main drawback of fossil fuels is pollution.Burning any fossil fuel produces carbon dioxide, which contributes to the "greenhouse effect", warming the Earth.Burning coal produces more carbon dioxide than burning oil or gas.It also produces sulphur dioxide, a gas that contributes to acid rain.We can reduce this before releasing the waste gases into the atmosphere.
15Disadvantages of fossil fuel for electricity (2) Mining coal can be difficult and dangerous. Strip mining destroys large areas of the landscape.(Instead of digging down in tunnels, the top layers are taken off and the coal is brought right to the surface)Coal-fired power stations need huge amounts of fuel, which means train-loads of coal almost constantly.This means covering a large area of countryside next to the power station with piles of coal.
16Is it renewable?Fossil fuels are not a renewable energy resource. Once we've burned them all, there isn't any more, and our consumption of fossil fuels has nearly doubled every 20 years since 1900.This is a particular problem for oil, because we also use it to make plastics and many other products.Ok, you could argue that fossil fuels are renewable because more coal seams and oil fields will be formed if we wait long enough.However that means waiting for many millions of years.That's a long time - we'd have to wait around for longer than the time that humans have existed so far!As far as we today are concerned, we're using it up very fast and it hardly gets replaced at all - so by any sensible human definition fossil fuels are not renewable.
17So the non-renewables will run out What can we use instead? We will always need electricity – so what primary sources can we use to make it?We will always need portable energy – for cars, mobile phones, places where there is no electrical grid – so what should we use instead?
18The government think nuclear is the next best thing Nuclear power is generated using Uranium, which is a metal mined in various parts of the world.The first large-scale nuclear power station opened at Calder Hall in Cumbria, England, in 1956.Some military ships and submarines have nuclear power plants for engines. Nuclear power produces around 11% of the world's energy needs, and produces huge amounts of energy from small amounts of fuel, without the pollution that you'd get from burning fossil fuels.
19How it worksNuclear power stations work in pretty much the same way as fossil fuel-burning stations, except that a "chain reaction" inside a nuclear reactor makes the heat instead.The reactor uses Uranium rods as fuel, and the heat is generated by nuclear fission.Neutrons smash into the nucleus of the uranium atoms, which split roughly in half and release energy in the form of heat.
20How it worksCarbon dioxide gas is pumped through the reactor to take the heat away, and the hot gas then heats water to make steam.The steam drives turbines which drive generators.In Britain, nuclear power stations are built on the coast, and use sea water for cooling the steam ready to be pumped round again. This means that they don't have the huge "cooling towers" seen at other power stations.
21Why do people worry about nuclear reactors? If something does go wrong in a really big way, much of the world could be affected - some radioactive dust (called "fallout") from the Chernobyl accident landed in the UK.With AGR reactors (the most common type in Britain) there are many safety systems, such as computers that can shut the system down if it begins to get too hot, flooding the reactor with nitrogen and/or water to absorb all the neutrons - although the water option means that reactor can never be restarted.
22DisadvantagesAlthough not much waste is produced, it is very, very dangerous. It must be sealed up and buried for many years to allow the radioactivity to die away.Nuclear power is reliable, but a lot of money has to be spent on safety - if it does go wrong, a nuclear accident can be a major disaster.Think about the tsunami in Japan last year - what happened then?People are increasingly concerned about this - in the 1990's nuclear power was the fastest-growing source of power in much of the world.In 2005 it was the second slowest-growing.
23But there are good points to it Nuclear power costs about the same as coal, so it's not expensive to make.Does not produce smoke or carbon dioxide, so it does not contribute to the greenhouse effect.Produces huge amounts of energy from small amounts of fuel.Produces small amounts of waste.Nuclear power is reliable.
24But nuclear is not renewable Once the uranium is used up there is no more.However, there is research looking at using sources other than uranium, which could extend the life of the idea almost indefinitelySo this is sometimes referred to as sustainable – meaning that we can go on using it as our use will not stop others doing so in the future
25We will look at these next time WindSolarBiomassWaterGeothermal
26But we also need to consider transport, as this is a major user of our energy resources The transport sector consumes 25% of energy production - and it does it inefficiently.At the most basic level, burning petrol is an efficient way of producing heat but an inefficient way of producing motion.Only a small percentage of the original energy is converted to energy of motion, the rest is waste heat.But worse than that, industry and the consumer do not seem to care that they are being inefficient.As long ago as 1985, Toyota produced a prototype vehicle with high fuel economy - of 82 miles per gallon, (or 19 miles to the litre) but the consumer market has not followed this innovation.
29Look at how many emissions are down to transport! Below is one of the possible alternative – not totally without controversy!But more about that next time too
30Homework I want some help with the lesson after half-term, please. Alternative sources of primary power that give us electricity:Solar, wind, waves, tides, hydroelectric from rivers, wind, geothermal and biomassAlternatives for transport:Fuel cells (they use hydrogen and oxygen to make water and release energy in the process) and biodeisal, and lastly electric cars (which could use green electricity to charge them)Heating:Solar heating and air source heat pumps
31What I want is enough for 3 slides For the alternative fuels:Slide 1 how it worksSlide 2 The good and the bad pointsSlide 3 Is there a future for it? – maybe a couple of piccies on slide 3There are links on the wiki for each examples
32The list Electricity from (a) Solar, (b) wind, (c) waves, (d) tides (e) hydroelectric from rivers,(f) wind,(g) geothermal(h) biomassTransport using(i) fuel cells(j) biodiesel using agricultural crops, e.g. sugar, maize, soya(k) biodiesel using non food plants(l) electric vehiclesHeating only(m) Solar water heating(n) Air source heat pumps